1. Field of the Invention
The subject invention relates to optical tables and more particularly to honeycomb tabletops for optical tables used in supporting precision laboratory equipment and vibration control, especially for use in clean rooms, and other similar environments.
2. Brief Description of the Background of the Invention
Honeycomb tabletops are typically used for supporting and positioning of highly sensitive scientific equipment, such as optical devices. Honeycomb tabletops generally include an upper skin, a lower skin, a honeycomb core, and a connecting side wall. The upper skin is typically provided with a plurality of tapped holes which are used for mounting equipment upon the tabletop surface. The honeycomb core maintains the structure rigidity and flatness of the upper skin so as to minimize the displacement of the devices relative to one anther. Historically, granite plates have been used as optical tables. However, their large weight and the difficulty of attaching components to their surfaces make them cumbersome to use.
Unfortunately, the tapped holes in the upper skin provide access to the cells of the honeycomb core in the interior of the optical table. Thus liquid or other debris spilled upon the table surface may pass into the interior. Due to the boned structure of the honeycomb and the complexity of the interior configuration, such spills are difficult and impractical to clean. Accordingly, conventional tabletops cannot satisfy the needs of usage in and maintenance of clean rooms.
Various methods of construction are known to solve these problems. Specifically, U.S. Pat. No. 4,621,006 discloses a tabletop design wherein a sealing sheet is positioned between a first distance honeycomb core portion adjoining the lower layer and a second distance several times honeycomb core portion adjoining the upper skin. The second distance is several times the mentioned first distance. So that the honeycomb core portion adjoining the lower layer is sealed off by the sealing sheet, and only a smaller distance of the honeycomb core portion needs to be cleaned.
U.S. Pat. No. 4,645,171 describes a honeycomb optical table wherein each hole in the top surface is sealed off from the interior of the honeycomb cells by a cavity enclosure which is secured to the underside of the top skin in connection with each hole. The cavity enclosures prevent the residue and contaminant from passing to the interior of the honeycomb core. As a result, cleanup can be effectively accomplished by wiping the table surface and applying suction to the small enclosure.
In U.S. Pat. No. 4,853,065 and U.S. Pat. No. 5,021,282, the use of a sealing sheet with projections corresponding in number and location to apertures in the table leavers and projecting into cells of honeycomb cores for a distance being several times smaller than the depth of such cores. It provides a means of sealing the holes of the upper layer from the honeycomb core.
U.S. Pat. No. 5,061,541 describes a honeycomb optical table with at least a layer of rigid corrugated material comprised of valleys and crests, an internal stiffening sheet, a drilled and tapped bar, and a series of connected cups to seal off from interior of the honeycomb cells which is secured to the underside of the top skin. The longitudinal axes of the crests and valleys of the said rigid corrugated material are aligned generally parallel to the both facing sheets and perpendicularly to the longitudinal axes of the cells of honeycomb core.
Another honeycomb optical table design is disclosed in U.S. Pat. No. 5,402,734, wherein a number of cups are positioned between the bottom layer and the top layer, and at least some of the cups are sized and shaped so as to cooperate with the lower face of the top layer to form a cavity surrounding at least two of the holes in the top layer so that contaminants will be unable to pass through the surrounding holes into the honeycomb core.
Although above-mentioned designs exhibit varying levels of effectiveness in containing the contaminants and spills easily and isolating from residue or contaminants entering the interior of the tabletop, no existing design appears to adequately address the need for easy and thorough cleaning of the portion of the tabletop exposed to the tapped holes.
In this invention, we describe an optical table having an easily-cleaned structure by using a downwards tread of object in field of gravity. Spillage, contaminants and residue can be more easily cleaned from the top down.